While still not as ubiquitous as Microsoft's Internet Explorer, Mozilla's new Firefox 3.5 browser was just released yesterday and is off to a great start. The browser was met with mostly positive reviews. Reuters stated, "There's no doubt that version 3.5 of Firefox is significantly faster than version 3...All in all, this is a major improvement over Firefox 3. Even if you're not currently a Firefox user, you'll want to give it a try."

CNET was slightly more measured commenting, "Firefox 3.5 is a much-needed improvement to the world's most popular alternative browser... While some of the improvements, such as the HTML5 and other developer enhancements will continue to make the browser their first choice, many of the other changes merely keep it in-line with the competition."

At the end of the day, though, Firefox 3.5's hot new features like HTML5 support and a faster JavaScript engine won over users. Downloads were blazing at 100 per second for much of the day yesterday. Mozilla's servers performed admirably under the load.

The new browser hit 1 million downloads within a couple hours and 2 million downloads in 7 and 1/2 hours. By this morning it had 4.3 million downloads. You can view the progress yourself on the download tracker found here.

The U.S. leads the world with 1.1 million downloads, with Germany in second with 496,000 downloads.

While the new Firefox is certainly very popular, it failed to surpass its own Guinness World record set by Firefox 3, which recorded 8 million downloads worldwide in 24 hours. Firefox also faces reinvigorated competition -- Apple claims that 11 million copies of its new Safari were downloaded in 3 days, and Opera is gearing up for a big 10.0 release.

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